1. Field of the Invention
The present invention relates to a system for producing three dimensional (3D) dynamic images.
2. Description of the Background Art
In recent years, computer graphics (CG) are often utilized for simulating the external appearance, the interior, and the lighting of buildings, etc. In addition, CG animation is widely utilized in the video media such as motion pictures and TV commercial messages. The system used in these cases has an interface enabling the operator to specify the viewpoint meticulously in each scene by using a video camera model imitating the real world, but such a system is designed for use by the specialized operator, so that for a general user without any specialized knowledge concerning the CG, the camera control, and the video production, it is quite difficult to operate this system properly and it usually requires numerous trials and errors.
On the other hand, in the field of virtual reality (VR), interactive operation is regarded as important, so that there is a function for enabling the user to freely walk around the virtual world by using the various 3D input devices such as a 3D mouse. Therefore, in VR, the user can produce the realistic video images as if the user is in a position of a cameraman using a portable video camera. However, the 3D input devices are still associated with the problems of precision and naturalness of the inner force sense feedback, so that it is still not so easy to master its handling and the unfamiliar user is unlikely to be able to handle it accurately. In the simulator of the automobile or the airplane, exactly the same movements as in reality can be obtained by exactly the same operations as in reality, so that the desired video images cannot be obtained unless the user has sufficient operation skills in reality. In the simulation game machine, the degrees of freedom in directions or ranges of movements are limited in order to make it possible for a general user to enjoy the game playing, so that the operation is relatively easier than the case of unlimited degrees of freedom, but truly realistic video images are not necessarily obtainable.
Normally, the video images are produced for the purpose of either recording necessary information or for creating some effect, but the majority of the cases in which a general user uses the video camera are in the former category, and in this type of the video camera usage, it is important to be able to capture a target object in a proper size from a proper angle in each scene and provide a natural sense of continuation in the successive scenes. However, it is still difficult for a general user to have full command of these aspects by means of the conventionally available interface. In particular, in a case where the target object is moving, the often encountered difficulties include a situation in which the target object becomes invisible as it is hidden behind the other objects, and a situation in which the target object is focused too closely such that it becomes impossible to tell which way the target object is viewed from.
In short, in the conventionally available system, it has been impossible for a general user to obtain the satisfactory video images, especially in a case of producing the dynamic images, by simply following the target object by the video camera.